<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .main1{
            height: 500px;
            display: flex;
            /*flex-direction: row-reverse;*/
            /*flex-wrap: wrap-reverse;*/
            flex-flow: row wrap;
            justify-content: center;
            align-items: center;
            /*align-content: flex-end;*/
        }
        .left,.middle,.right{
            width: 30%;
            height: 150px;
        }
        .left{
            background-color: orange;
        }
        .middle{
            background-color: orangered;
        }
        .right{
            background-color: deepskyblue;
        }
        .main{
            width: 500px;
            height: 350px;
            position: fixed;
            top: 0;
            left: 0;
            right: 0;
            bottom: 0;
            background: red;
            margin: auto;
        }
    </style>
</head>
<body>
<div class="main">
<!--    <div class="left"></div>-->
<!--    <div class="middle"></div>-->
<!--    <div class="right"></div>-->
</div>

</body>
<script>

</script>
</html>










